Spray guns and torches are well known in which heat fusible material in finally divided particulate form is fed into a zone where the material is heat-softened or melted and sprayed onto a surface to be coated. The heat fusible material is ordinarily referred to as powder. Such guns or torches are composed of two main parts, namely, an upper body member which supports an electrode and a lower body member which supports tubes and other parts for forming an arc with the electrode and injecting powder with an inert gas under pressure. Both upper and lower body members are conventionally made of metal and operate at different electrical potentials. It is necessary, therefore, to provide insulators between the two body members. High temperatures of operation also require the incorporation of a cooling system. Conventional torch constructions commonly use O-rings or fluid seals to contain the coolant which is circulated through passages within each body member.